The increasing size and flexibility of wind turbine blades introduce significant aeroelastic effects, potentially causing aeroelastic instability such as edgewise instability and flutter. Current linear models, based on small deflection assumptions, are inadequate for modern large blades that experience significant geometric nonlinearities. Existing cross-sectional analysis models also face issues of inaccuracy and inefficiency.This book develops two key advancements: 1) a cross-sectional model using classical lamination theory and extended Bredt-Batho shear flow theory to accurately and efficiently determine composite blade properties; 2) a nonlinear aeroelastic model incorporating geometrically exact beam theory and a comprehensive load model.Validated through MATLAB and COMSOL Multiphysics, these models show excellent agreement with experimental data. Application to the WindPACT 1.5MW blade reveals reduced flapwise deflection and highlights the higher risk of edgewise instability, underscoring the importance of proper rotor speeds. This book offers vital insights and advanced models for developing reliable, efficient next-generation wind turbines.